I'm trying to build a trailer for a Tandem Island by converting my 4'x8' Harbor Freight trailer. The plan is put a removable storage box over the TI. When we go camping the box is in place; if we are only going for a daysail the box remains at home.

The boat is on order so I can't measure it myself. What I'm interested in knowing is how much clearance do I need UNDER THE BOX for the TI to fit. So the measurement I'm after is the height of the boat from the low point to the top of the high point on the hull; I assume this is the top of the akas.